A conventional energy distribution forming method disclosed in, for example, "Denki Gakkai Magunetikkusu Kenkyukai Shiryo", MAG-94-26, pp. 63-69 (1994) is called a sampled pattern matching method (hereinafter abbreviated to "SPM method").
The SPM method is employed for determining a distribution pattern of an energy source forming a desired field when a distribution (electric field distribution, magnetic field distribution, radiation intensity distribution, temperature distribution or the like) in the desired field is given. To put it concretely, the SPM method arranges lattice points in a space and makes sequential search to find a point which makes an energy source assumed to be at that point form a pattern close to the distribution of the desired field. Search is terminated upon the increase of the coincidence degree of the pattern created by the energy source with the distribution of the desired field to a maximum.
The pattern coincidence degree is evaluated by an angle .theta. made between a measured distribution pattern vector V and a calculated distribution pattern vector U. Concretely, pattern coincidence degree is defined by the following equality (1): EQU .gamma.=cos .theta.=U.multidot.V/(.vertline.U.vertline..vertline.V.vertline.) (1)
where U.multidot.V is inner product, and .vertline.U.vertline. and .vertline.V.vertline. indicate the respective magnitudes of the vectors U and V.
FIG. 1(a) shows a desired magnetic field distribution 101, and FIG. 1(b) shows an arc-shaped coil 102 having the shape of a circular arc for creating a magnetic field distribution close to the desired magnetic field distribution estimated by the SPM method. FIG. 1(c) shows a magnetic field distribution 103 formed by the arc-shaped coil 102 in FIG. 1(b). The size of the circle is illustrated to be proportional to magnetic field intensity. The magnetic field distribution 103 realizes approximately the same as the magnetic field pattern shown in FIG. 1(a), which proves the effectiveness of the SPM method. It should be noted that constant current must be supplied to the coil because the foregoing method only distributes unit current sources and is unable to vary the amplitude of the current in principle.
Since the conventional method of forming an energy distribution is thus constructed, the position of an energy source having a fixed intensity can be determined, but there remains a problem the intensity of the energy source is invariable.
The present invention has been made to solve the foregoing problem and it is therefore an object of the present invention to provide an energy distribution forming method capable of varying the intensity of energy source distribution.